Energy: the capacity to effect change BCOR 011

Lecture 11

Two types of energy

Chapter 8

The Flow of Energy in a Cell Sept 26, 2005

Potential Energy

Kinetic Energy

-stored in height

-energy of movement

-stored in battery (conc/charge) -stored in BONDS

-molecules colliding, vibrating -HEAT, light

1

2

Figure 8.1

1st Law of Thermodynamics

Potential Energy Stored in:

Figure 8.2

location

Energy is neither created nor destroyed in chemical reactions but only Transformed from one form to another

Figure 8.5

On the platform, a diver Diving converts potential has more potential energy. energy to kinetic energy.

Chemical bonds

Potential

Potential

Kinetic

Kinetic

gradient Climbing up converts kinetic energy of muscle movement to potential energy.

In the water, a diver has less potential energy.

3

4

In a chemical reaction products have a lower potential energy than reactants

a Chemical Reaction

Atoms bonded in High Potential Energy Configuration

Example

- -

Energy is Released

H

H-C-H H

Atoms bonded in Low Potential Energy Configuration

Reorganization of Bonds of existing molecules - an exchange

O=C=O

O=O H

O=O

Same # of H’s Same # of C’s Same # of O’s

O

H

H

H -

H-C-H H

6

Energy that is released:

reduced

Has the capacity to DO WORK

O=O

Raise potential state of something else

O=C=O

H

O

H

ENERGY RELEASED

Or effect movement – heat, motion

oxidized Low Energy

7

H

All Start with filled outer shell of electrons All End with outer shell of electrons

5

High Energy

O

8

Other Types of Work

Types of Work: 1

Biosynthetic: changes in chemical bonds

A + B

2. Chemical Concentration Gradient

C + D products

reactants

A+B G+H E+F

C+D

Ainside + Boutside

even

even

even

low

high

9

3. Electrical work – movement of ions across a membrane against an electrochemical gradient

Ainside + Boutside

even

Aoutside + Binside

10

Other Types of Work

Aoutside + Binside

+

-

11

4

Mechanical Work: Movement, Motility

12

• Some organisms Another form of MOVEMENT

Relaxed Low Energy Conformation

A

– Convert energy to light, as in bioluminescence

Conformation

B

Poised 13 High Energy

Figure 8.1

Change In potential Energy

Energy that is released:

State 1

Has the capacity to DO WORK Raise potential state of something else Or effect movement – heat, motion But some is always lost to disorder

State 2

Gross Pay 15

14

Released Energy

Ability To do + Randomness work

Take Home + Pay

Taxes 16

Kinetic Energy can be dissipated:

Second law of Thermodynamics:

Randomized

Releases Energy

Kinetic Energy Ch an ce

of

Sound Floor Vibration go ing

in

RE

Requires Energy Input

VE

RS E?

Disorder

The Universe is proceeding to a State of MAXIMUM DISORDER

Only time this is not true is when no movement anymore ie. at abosolute zero 17

18

Change In potential Energy

0o K - no motion, no “taxes”

State 1 A Progressive Scale: Higher the temperature,

the more that disorder comes into play higher proportion of energy lost to randomness

19

State 2

Enthalpy ∆H

Released Energy

Ability To do + Randomness work Free Energy + ∆G

Entropy T ∆S

20

ENTROPY ∆S (disorder)

ENTHALPY ∆H Change in Chemical Bond Energy

Freedom of Movement or Position

Time

21

Number of possible states that can be present in:

Change in Freedom

Roll of “2”

High Potential

High Potential

Randomness

ENTROPY ∆S

Change in Chemical Bond Energy

ENTHALPY ∆H

Low entropy Only 1 possible “state”

Low Potential

Glucose + 6 O2

6 CO2 + 6 H2O

ENTROPY ∆S Few States

Low Potential

6 Glucose 6 CO2 + + 6 O2 6 H2O

Change in Freedom

Many States “Dispersed”

22

Number of Possible States That can be Present in Few States

Many States “Dispersed”

time

Roll of “7”

High entropy

-∆H

6 possible “states” 23

Na+ ClNaCl crystal ions in water

Na+ ClNaCl crystal ions in water

+∆S

24

Change in Chemical Bond Energy

The Free Energy Change ∆G Dictates whether a reaction will Proceed spontaneously or not

Energy that Goes to Do Useful Work

Energy that Goes to Randomness Dependent On Entropy Temperature

Enthalpy

“free energy” (Gibb’s Free Energy)

Kinetic Movement

Whether a Reaction is

∆H

Favorable or Unfavorable

=

T∆S

∆G 25

=

+

∆H -

If ∆G = negative # reaction is energetically favorable

∆G

T∆ S “spontaneous” 26

An exergonic reaction – Proceeds with a net release of free energy and is spontaneous “will happen” Reactants

Free energy

Amount of energy released (∆G 0)

Energy

Oxidized

Reactants

The sum of these is the Progress of the reaction

Figure 8.6

Complex

change in Entropy

Lower

8

fats

H H-C-H H

H R-C-OH H

alcohol

30

EXERGONIC REACTIONS gasoline burns iron rusts hydrogen and oxygen form water (explosive!)

Either: go to bonding arrangement with lower potential energy O =

sugars

R-C-H aldehyde

O =

change in Bond Energy

hydrocarbon

net ENERGY RELEASED - EXERGONIC = FAVORABLE If require net ENERGY INPUT - ENDERGONIC = UNFAVORABLE

Simple

Reduced (no oxygens) H H HHH HH H H-C-C-C-C-C-C-C-C-H H HH HH HH H

Net Useful Energy (∆ (∆G)

If

(b) Endergonic reaction: energy required

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High

Simple

R-C-OH

Final product

acid

Or: go from a more complex state to a simpler state 1 molecule of 8 carbons

vs

8 molecules of 1 carbon

O=C=O

Low

Oxidized

Carbon 31 dioxide

Lowest

32

∆H= ∆S= + ∆G= very -

favorable favorable favorable

2 Spontaneous 33 Favorable - it can happen

∆H= ∆S= ∆G=

Unfavorable + + Very favorable favorable

Entropy Driven Reaction Spontaneous Favorable - it can happen 35 Entropy overwhelms Enthalpy

∆H = Hproducts -Hreactants − ∆H exothermic Heat released + ∆H endothermic Heat input icepack

34

∆H= ∆S= ∆G=

-

very favorable unfavorable favorable

Enthalpy Driven Reaction Spontaneous Favorable - it can happen 36 Enthalpy overweighs Entropy

∆H= ∆S= ∆G=

∆G = ∆H – T∆S ∆G = ∆H – T∆S ∆G = ∆H – T∆S (-) - (+) (- ) - (- ) (+) - (+) Spontaneous Enthalpically Entropically 37 Favorable Rxn Driven Rxn Driven Rxn

A typical ENDERGONIC/Unfavorable/NonSpontaneous REACTION - building a polymer Monomer + Monomer

+ +

unfavorable unfavorable unfavorable

Non-spontaneous

NOT Favorable - it can NOT happen 38

COUPLED Reactions

Tie a favorable rxn with An otherwise unfavorable rxn

Polymer + Water

Requires 5.5 energy units

WILL NOT OCCUR How could we make it occur? If have a captured packet of energy of 7.3 energy units

Integrate

an exergonic reaction with an endergonic reaction

39

Drive otherwise unfavorable reactions 40

∆G = +5.5 kcal/mole

1.

2. ATP+ H2O

ADP + Pi

ATP

∆G = -7.3 kcal/mole

ADP + Pi Favorable or unfavorable41 ?

Coupled Reaction ADP -P (ATP)

Note: Each step is favorable

∆G = -7.3 kcal/mole +∆G = +5.5 kcal/mole Net rxn ∆G = -1.8 kcal/mole 42

Another Example of a Coupled Reaction

+ monomer1

ADP-monomer1

+ P Endergonic reaction: ∆G is positive, reaction is not spontaneous

I’m free! ∆G = -1.0

ADP-monomer1 + monomer 2

NH2

Now tied together Glu

ADP

+

Glutamic acid

monomer1-monomer 2

Now I’m free too! ∆G = -0.8 7.3 units released Net: ATP +H2O monomer1 + monomer2 5.5 units needed

+

NH3

Glu

Ammonia

Glutamine

∆G = +3.4 kcal/mol

Exergonic reaction: ∆ G is negative, reaction is spontaneous

ATP

ADP + P monomer1-monomer2 + H2O

DO NOT LET ATP FALL APART IN 1 STEP, use energy in its bond to MAKE the polymer linkage

43

Figure 8.10

+ H2 O

ADP +

Coupled reactions: Overall ∆G is negative; together, reactions are spontaneous

P

∆G = + 7.3 kcal/mol

∆G = –3.9 kcal/mol

44

Three types of cellular work powered by ATP hydrolysis Physical movement

P

Equilibrium Reactions in a closed system

i

P

Motor protein

Driving Conformational Changes ADP Of + P Proteins

Protein moved

(a) Mechanical work: ATP phosphorylates motor proteins Membrane protein

ActiveATP Transport Pumps

– Eventually reach equilibrium ∆G < 0

∆G = 0

i

P

Solute

P

i

Solute transported

(b) Transport work: ATP phosphorylates transport proteins

P

Glu +

NH2 NH3

Reactants: Glutamic acid and ammonia

Figure 8.11

+

P

Glu

i

Product (glutamine) made

Biosynthetic Coupled Rxn45

Figure 8.7 A

(a) A closed hydroelectric system. Water flowing downhill turns a turbine that drives a generator providing electricity to a light bulb, but only until the system reaches equilibrium.

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(c) Chemical work: ATP phosphorylates key reactants

In living systems

cellular respiration is a series of favorable reactions

– Experience a constant flow of materials in – Constant Energy Input ∆G < 0 ∆G < 0 ∆G < 0

∆G < 0 (b) An open hydroelectric system. Flowing water keeps driving the generator because intake and outflow of water keep the system from reaching equlibrium.

Figure 8.7 Figure 8.7

47

(c) A multistep open hydroelectric system. Cellular respiration is analogous to this system: Glucoce is brocken down in a series of exergonic reactions that power the work of the cell. The product of each reaction becomes the reactant for the next, so no reaction reaches equilibrium. 48

Summary:

For example, oxidation of glucose: C6H12O6 (glucose) + 6O2

6CO2 + 6H2O

-matter is neither created nor destroyed -the universe is proceeding toward disorder

∆G= -686 kcal/mol

∆H = -673 kcal/mol

∆H = enthalpy (heat content,bond energy)

T∆S= -13 kcal/mol

∆S = entropy (randomness)

in the cell, this is done in >21 steps!

∆G = free energy (available to do work)

Capture the energy in small packets

∆G = ∆H - T∆S

ie, 36 ATP units of 7.3 kcal

- coupled reactions

49

-biological systems always need constant energy input

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